This invention concerns a chair, especially an office chair, with a vertical column, a seat mounted on this column and a backrest that is connected to said column by a curved supporting bar plus three horizontal transverse axes which connect the chair and the column, the column and the curved supporting bar and the curved supporting bar and the seat in a hinged triangular arrangement and at least one of the transverse axes permits a relative shift in the connected parts.
The adjustment mechanism of such a chair is essentially known to the present applicant from European Patent Application No. 80 100456.5. It offers the advantage that the seat and the backrest can be moved simultaneously, i.e., with a handle, and in this movement the backrest covers a greater distance than the seat, as is desirable in adjustable chairs for reasons of comfort and ergonomy. The known adjusting mechanism, however, can be regarded as a disadvantage at least inasmuch as the three required transverse axes are relatively massive and expensive to produce if premature wear is to be avoided, which would lead to an unpleasant and insecure sensation on sitting in the chair. Special difficulties in this regard can arise in manufacturing a transverse axis which permits a parallel shift with respect to itself. These difficulties are not insurmountable, but they do lead to a rather complex design which may also require a certain amount of care which is not justified in all cases.
This invention is therefore based on the goal of designing a chair of this type which will permit a simple and sturdy construction while maintaining the ergonomic and technical handling advantages of the known solution.
This goal is achieved according to this invention with a chair of the type described initially where at least one of the transverse axes which connects the seat with the column and the curved supporting bar is formed by rubber pads which support the chair on the column and/or the curved supporting bar.
Rubber pads in the present connection are understood to refer to elastomer blocks of a rubbery material without being limited to rubber in the narrower sense. Rubber-metal composite constructions are also possible. Rubber pads as understood in this sense permit the relatively slight swiveling movements of the seat with respect to the column and the curved supporting bar of the backrest while also absorbing the shifting movements in displacement of the above-mentioned hinged triangular arrangement as will be discussed again below with reference to the figure.
In a preferred version, the two transverse axes connecting the seat with the column and the curved supporting bar are formed by rubber pads which offer the additional advantage that they support the seat with a certain spring action. The rubber pads may be attached by means of screws, glue or some other means.
With the preferred design described above, the usual axial bearing is necessary only for one horizontal transverse axis, namely the horizontal transverse axis between the curved supporting bar of the backrest and the column. The swiveling movement of the curved supporting bar about this transverse axis can preferably be stopped in various angle positions. This offers the possibility of adjusting the backrest as well as the seat in various angle positions. This locking in a given position can be accomplished with the help of a catch which engages a toothed segment or a pin which engages a plate segment which has holes, or by some other mechanical means, or even with the help of a pneumatic spring.
Preferably, the curved supporting bar of the backrest and thus also the seat are subject to a pretension acting toward the front of the chair by means of a rubber buffer which functions as a spring. This rubber buffer is located in a suitable position between the column or a projecting arm which projects forward from the column and the curved supporting bar.